Focus Interview丨Three-dimensional monitoring of "sky and ground" to protect flood control safety
Recently, heavy rainfall has continued in many parts of the south, floods and geological disasters have occurred in Guangdong, Fujian and other places, causing casualties and property losses. Drought has developed rapidly in some parts of the north, with obvious characteristics of floods in the south and droughts in the north. On June 18, General Secretary Xi Jinping issued important instructions on flood control and drought relief. He called for all-out response to the disaster. He stressed the need to strengthen disaster monitoring and early warning, investigate risks and hidden dangers, prepare sufficient equipment and materials, improve work plans, effectively respond to various emergencies, and effectively protect the safety of people's lives and property and the stability of the overall social situation. How to strengthen forecasting and early warning to prevent disasters before they happen?
Heavy rain is a force of nature that we cannot resist, but if we can forecast the arrival of floods in time when the rainstorm comes, we can minimize casualties and property losses.
Wang Lin, chief hydrology forecaster at the Ministry of Water Resources: We need to defend against extreme rainfall and extreme rainstorms caused by extreme climate conditions. Some small watersheds may have new floods within an hour or two. At this time, it is difficult to make timely forecasts and issue warnings based on the rainfall forecast alone. How can we extend the flood forecast period, flood forecast period and improve the accuracy of flood forecasts? Through modern monitoring methods, we can enhance the overall ability to defend against natural disasters.
Residents living near Lugou Bridge in Beijing may have discovered that a tall iron tower was erected here this year, with a detector constantly rotating on the top of the tower.
Du Longgang, deputy director of Beijing Hydrological Station: This radar is mainly used for rainfall monitoring. Unlike traditional meteorological radars, it only monitors water vapor between 0 and 2 kilometers and infers rainfall that may fall to the ground. Water vapor within 2 kilometers above the ground can basically fall to the ground.
In recent years, the water conservancy department has been pushing forward the construction of the "three lines of defense" for rainwater monitoring and forecasting. The basic components of the first line of defense are meteorological satellites and rain radars, the basic components of the second line of defense are rain gauges, and the basic components of the third line of defense are hydrological stations. These "three lines of defense" use three-dimensional monitoring methods of "sky and ground" to monitor and forecast rainwater conditions in the basin in real time, so as to take timely measures to deal with possible flood disasters. The three networked rain radars are an important part of the "first line of defense" for flood forecasting in the Guanting Gorge area of Beijing, that is, the Yongding River Basin.
The Yongding River flows through the Guanting Gorge area. Through rainfall radar and model calculations, the water content in the clouds and the possible precipitation in the area can be accurately predicted 1 to 3 hours in advance. This has a relatively strong predictive ability for whether a flood will form and how big the flood will be. If the first line of defense is to "move the checkpoint forward and push the defense line outward", then strengthening the second line of defense is to improve the accuracy of forecasts and the effectiveness of early warnings.
Du Longgang, deputy director of Beijing Hydrological Station: Traditional rain gauges have a measuring cylinder at the bottom, which is taken indoors to measure the water content. They measure the amount of rain once an hour or once a day. Generally, they are checked at least once an hour. High-precision and advanced rain gauges sense how much rain is likely to fall through changes in weight, with an accuracy of 0.1 mm. They are very timely and send out rain gauges as soon as it rains, at the minute level.
Water flows to lower places. Usually, mountainous areas are full of gullies. Once a rainstorm comes, each gully may collect ground rainwater in a short period of time to form a flash flood, and the floods in the gullies will quickly converge into the main stream to form a flood peak. Therefore, it is also very important to accurately measure the precipitation conditions of each rain and flood gully that may form a flash flood. This is the "second line of defense" for flood prediction and forecasting. That is, when the first line of defense accurately predicts the "rain in the cloud", it is also necessary to accurately monitor the real-time data of the "rain on the ground", so that the model can be calculated to more accurately predict whether a flood will form and the flow of the flood.
Du Longgang, deputy director of Beijing Hydrological Station: In the past, Beijing Water Affairs Bureau used 245 rain gauges. This year, we have increased the number of rain gauges to more than 1,900 by encrypting and integrating the rain gauges of the meteorological department and Beijing Municipal Planning and Natural Resources Commission.
The reason why such dense rainfall measurement points have been established in the second line of defense can be clearly seen from a picture: the Yongding River flows through the Guanting Gorge area, which is densely covered with ravines. When heavy rains come, each ravine is a rainwater flood ditch and may cause floods.
Wang Yajuan, deputy director of Beijing Hydrological Station: In the past, there were only 29 rain gauges. Now, there are 256 rain gauges in the entire Guanting Gorge, and further plans are in place for a total of 384. In the future, the station network density in Guanting Gorge will be able to reach 2.5 square kilometers per station. In this way, we can prepare in advance and provide data and decision-making support for its downstream.
Rain gauges have been set up in many rainwater ditches, which greatly enhances the monitoring capability of the second line of defense for "falling rain". In a river basin, floods from rainwater ditches and tributaries will eventually flow into the main stream to form a flood peak. The hydrological stations distributed upstream and downstream are the forefront of accurately measuring the flood peak flow when the flood arrives, and are also the "third line of defense" for flood prediction and forecasting.
Wang Yajuan, deputy director of Beijing Hydrological Center: The total length of the river from Yanchi to Longjiazhuang hydrological station is 34.2 kilometers. The flood takes two hours to evolve. The flood from Longjiazhuang to Sanjiadian takes one hour. The flood from Sanjiadian to Lugou Bridge takes one hour. This provides advance flood control scheduling, flood control decision-making, and data support for the flood diversion hub at Lugou Bridge downstream, and also serves as a forward warning.
When heavy rains come, once floods are formed, the flood flow will gradually increase from upstream to downstream. Therefore, the more accurate the monitoring of floods by hydrological stations along the way, the more accurate the basis for flood control command can be. Therefore, the hydrological stations of the third line of defense have the function of "bottom line defense". So far, 33 hydrological stations have been distributed in the Yongding River Basin from upstream to downstream.
Zhai Teng, director of Longjiazhuang Hydrological Station of Beijing Urban Rivers and Lakes Management Office: "We can grasp the peak flow. We need to provide data guarantee for the Sanjiadian Water Conservancy Project downstream. Only by grasping the peak point can the flood discharge safety of the Sanjiadian Water Conservancy Project be effectively guaranteed."
Because the hydrological station is at the forefront of the approaching flood, the monitoring equipment must be more advanced and more robust, and also equipped with satellite communication facilities.
Establishing the "three lines of defense" and accurately measuring the "three lines of defense" to calculate accurate data on flood formation and evolution, so as to achieve "measurement, accurate measurement, grasp and report", will greatly improve the ability of flood forecasting, early warning, rehearsal and emergency plan, and buy time for evacuating people and protecting property before the disaster. Once continuous heavy rainfall occurs and it is predicted that a major catastrophic flood may form, the flood control headquarters will initiate an emergency response.
Zhu Jinliang, deputy director of the Beijing Water Affairs Emergency Center: We issued flood warnings, mountain torrents and waterlogging risk warnings 48 hours in advance, and initiated a level 1 emergency response for flood control and drainage 24 hours in advance. This is the highest level of emergency response in the water affairs system. The people were transferred multiple times, twice, and three times according to the principle of expanding the area. We carried out reservoir pre-discharge scheduling in advance, lowered the river water level in advance, and freed up reservoir capacity.
Flood forecasts, warnings, rehearsals, and emergency plans will be transmitted from the Beijing Flood Control Headquarters to the district governments at the first opportunity, and then quickly to the towns and villages. Jiuyuan Village, Wangping Town, Mentougou District, Beijing is located in a mountain valley in the upper reaches of the Yongding River Basin. Once a mountain torrent is about to come, the emergency plan will be activated. If a flood is about to come, the first priority is to evacuate people, so multiple early warning systems have been built in rural areas of Mentougou, Beijing, to ensure the safety of people.
Wang Zhibin, a village cadre of Jiuyuan Village, Wangping Town, Mentougou District, Beijing: The flood control assistant is also called a home alarm. It is connected to the simple rain gauge upstairs. If it rains 52 mm within an hour, it will trigger the order to prepare for evacuation. If it rains 65 mm within an hour, it will trigger the order to evacuate immediately. The urgent language is "evacuate immediately, evacuate immediately". We also installed an integrated sound and light alarm device this time. When the flow rate, flow rate and depth of the river reach its warning level, it will trigger a sound and light alarm, indicating that the river has basically reached the flood level.
Beijing has reinforced stormwater ditches and installed automatic alarm facilities in mountainous areas like Jiuyuan Village. Each township and village has also clarified the action measures after the higher-level authorities issue disaster warnings. Disaster prevention work has become more standardized and the linkage mechanisms of various links have become more sound.
The "three lines of defense" of rainwater monitoring and forecasting are interconnected and complementary. Building a modern rainwater monitoring and forecasting system will comprehensively enhance my country's water security capabilities. On May 20, the 10th World Water Forum opened in Indonesia. China's water management concepts and disaster reduction and prevention practices were highly praised by experts and scholars from many countries.
Liu Zhiyu, Deputy Director and First-Class Inspector of the Hydrology Department of the Ministry of Water Resources: General Secretary Xi Jinping attaches great importance to flood and drought prevention work, and repeatedly emphasizes the need to effectively protect the lives and property of the people and put it first. He has repeatedly proposed to strengthen monitoring, forecasting and early warning, and make up for the shortcomings of disaster early warning and monitoring. Accelerating the construction of the "three lines of defense" for rain and water monitoring and forecasting is a political requirement for implementing the important instructions and instructions of General Secretary Xi Jinping, an urgent need to win the modern defense war and defend the bottom line of flood and drought prevention, and an inevitable requirement for promoting high-quality development of water conservancy.
my country has a vast territory and complex terrain. In addition to large rivers, there are also many regional rivers. Floods are like beasts with great power. Disaster prevention and mitigation start with prevention. We should accelerate the construction of the "three lines of defense" for rainwater monitoring and forecasting, and ensure water safety. When extreme weather comes, we can measure the rainfall accurately in advance and report floods, so as to better protect the safety of people's lives and property.
